/* 绝对定位垂直居中对齐 */
.abs-center(@type: absolute) {
    position: @type;
    left: 50%;
    top: 50%;
    transform: translateX(-50%) translateY(-50%);
  }
  
  .container {
    position: relative;
    .item {
      @size: 100px;
      width: @size;
      height: @size;
      .abs-center(fixed);
    }
  }
  